Govindaraj, L.Arumugam, S.Thiyagarajan, R.Kumar, Dinesh...
7页查看更多>>摘要：Diamond is an excellent wide-bandgap electrical insulator. However, boron (B) doping is known to induce superconductivity in diamonds. We have performed electrical transport and magnetic measurements under pressure with doping concentrations of (1.4 and 2.6) x 10(21) cm(-3), in a temperature range 2 - 10 K and present two interesting effects in superconducting B doped diamond (BDD) thin films: (i) Wohlleben effect (paramagnetic Meissner effect, PME) and (ii) pressure-induced spin glass-like susceptibility anomaly. PME, a low field anomaly in inhomogeneous superconductors, could arise from flux trapping, flux compression, or for non-trivial reason such as emergent Josephson pi junctions. The joint occurrence of PME and spin glass type anomalies points to the possible emergence of pi junctions. BDD is a disordered s-wave superconductor; and pi junctions could be produced by spin-flip scattering of spin 'A moments when present at weak superconducting regions. A frustrated network of 0 and pi junctions will result in a distribution of spontaneous equilibrium supercurrents, a spin glass (phase glass) state. Anderson localized spin 'A spinons embedded in a metallic fluid (two-fluid model) could create pi junction by spin-flip scattering. Our findings are consistent with the presence of pi junctions, invoked to explain the observation of certain resistance anomaly in BDD.
原文链接:
NSTL
Elsevier
Xie, YimingZheng, HengkangWang, GuangdaHuang, Ziyi...
9页查看更多>>摘要：An 8 T no-insulation (NI) high temperature superconducting (HTS) insert has been designed using a 12 T low temperature superconducting (LTS) magnet to build a 20 T magnet. This paper focuses on the electromagnetic design and stress analysis of the 8 T HTS insert coil. The preserve elitist genetic algorithm was adopted to design a coil with the least cost in conjunction with the finite element program. The pre-stress during the winding, the thermal stress during the cooling down, and the electromagnetic stress considering screening current effect during the charging of the HTS insert coil were analyzed and discussed in this paper.
原文链接:- NSTL
- Elsevier
Roter, B.Ninkovic, N.Dordevic, S. V.
6页查看更多>>摘要：In this work we used unsupervised machine learning methods in order to find possible clustering structures in superconducting materials data sets. We used the SuperCon database, as well as our own data sets complied from literature, in order to explore how machine learning algorithms groups superconductors. Both conventional clustering methods like k-means, hierarchical or Gaussian mixtures, as well as clustering methods based on artificial neural networks like self-organizing maps, were used. For dimensionality reduction and visualization tSNE was found to be the best choice. Our results indicate that machine learning techniques can achieve, and in some cases exceed, human level performance. Calculations suggest that the clustering of superconducting materials works best when machine learning techniques are used in concert with human knowledge of superconductors. We also show that in order to resolve fine subcluster structure in the data, clustering of superconducting materials should be done in stages.
原文链接:- NSTL
- Elsevier
Haberkorn, N.Correa, V. F.
7页查看更多>>摘要：We study the vortex dynamics on beta-Bi2Pd single crystals with a superconducting critical temperature of 5.1 K. The upper critical fields and magnetic penetration depth are determined from magnetization measurements. At low temperatures, the self-field critical current density (Jc) is Re. 20 kA/cm2. The vortex pinning energy, extracted from an Anderson-Kim approximation, is between 340 K and 140 K for fields between 100 G and 600 G. Dif-ferential scanning calorimetric measurements show that the crystals start to transform into the alpha-phase at temperatures as low as 60 degrees C. Short annealing at 100 degrees C modifies the pinning landscape increasing Jc mainly at temperatures below 3 K. The angular dependence of Jc from electrical transport experiments shows a broad peak when the magnetic field is parallel to the crystallographic c-axis, indicating the presence of correlated disorder.
原文链接:- NSTL
- Elsevier
Zhu, JiaminTong, MingleiChen, SikanZhao, Yue...
6页查看更多>>摘要：Second generation HTS tape has entered the stage of mass production. The biggest bottleneck in stable production and consistently high-quality superconducting coatings lies in the control of deposition temperature during superconducting coatings. It is very challenging to effectively monitor the temperature in the dynamic process of roll-to-roll coating. Through observation, it is found that the color of superconducting surface is very sensitive to the change of coating temperature. In this study, a real-time video analysis technology has been developed to obtain the grayness scale of the surface of the superconducting layer during coating. The relationship between grayness scale, temperature and the final critical current of superconducting tape has been established through short sample experiments. These relationships are also clearly demonstrated in the long tape production process, which can significantly detect any abnormal trends of tape products by capturing the surface temperatures through grayness scale. The region of interest was tracked, by dividing it into three parts and calculating the average grayness level of each part. The results obtained can be used to determine PLD temperature setting and provide a reference for the subsequent slitting of superconducting tapes. This work also provides a potential quality improvement technique for superconducting tape production.
原文链接:- NSTL
- Elsevier
Askerzade, I. N.Askerbeyli, R. T.Ulku, I.
6页查看更多>>摘要：The escape rate of S -> R switching (from superconducting S state to unstable resistive R state) in an ac SQUID on Josephson junction with unconventional current-phase relation was investigated. We used two types of currentphase relations with additional terms to the first harmonic sin phi: a case of the second harmonic sin2 phi and a case of the fractional term sin(phi/2). It was shown that escape rate can exhibit qualitative features in the case of junctions with unconventional current-phase relations.
原文链接:- NSTL
- Elsevier
Kim, G.Kim, I. S.Choi, I. M.
6页查看更多>>摘要：Korea Research Institute of Standards and Science (KRISS) has started to design a Superconducting Gravimeter system based on a SQUID sensor. In this paper, we describe the design and fabrication of fundamental components of the superconducting circuit. Heat switches (HSWs) were fabricated using surface-mounted device (SMD) resistors and niobium (Nb) wires in a variety of ways to provide DC current to superconducting coils. The HSWs were tested regarding response time, wave form, and aging features at a cryogenic temperature (4.2 K) for 40 days. These results allowed us to optimize the HSW designs, superconducting housing, and superconducting circuits of the system. The system was designed as a drive controller to inject constant current into the superconducting coils and to control the operating times of the HSWs and the constant current. In addition, we also describe a suitable method for calculating the inductance of the closed superconducting loops.
原文链接:- NSTL
- Elsevier
Niu, MinghuiShi, WeifengYing, LiliangWang, Zhen...
5页查看更多>>摘要：Current-voltage (I-V) characteristics of shunted Nb/Al-AlOx/Nb Josephson junctions (JJs) can be precisely described in the resistive capacitive inductive shunted junction (RCLSJ) model derived from resistive capacitive shunted junction (RCSJ) model with additional parasitic inductance. However, the methods for extraction of current values in the RCLSJ model are not fully developed, which causes unsatisfactor accuracy of the simulations of superconducting integrated circuits. In this work, we propose an innovative method for extraction of parameters that is capable to solve inaccuracy problem. The enhancement is achieved by including the fluctuation of device parameters due to fabrication process in the analysis. A Josephson comparator is designed in the RCLSJ model to test the performance of the proposed parameter extraction method. Obtained results show that our method ensures 2 to 3 times higher simulation accuracy at frequencies above 60 GHz as compared to the traditional method.
原文链接:- NSTL
- Elsevier
Liao, FuhuiLin, JianhuaFarid, Muhammad AsimChen, Yuxuan...
6页查看更多>>摘要：The potassium and lanthanum co-doped superconducting series with composition Ba1-xLax/4K3x/4(Bi0.25Pb0.75) O3-delta where (0.00 <= x <= 0.40) has been synthesized by solid state reaction. Their crystal structure and super-conducting properties has been investigated in detail. All the synthesized samples crystallize in P1 space group as confirmed by the X-ray diffraction analysis. All the samples show sharp superconductivity transitions as confirmed from electrical resistivity measurements. Significantly the T-c(onset) (the highest temperature at which the electrical resistivity decreases abruptly) ranges from 11.4 to 11.8 K and T-c(zero) (the highest temperature at which the electrical resistivity becomes zero) ranges from 10.7 to 11.2 K.
原文链接:- NSTL
- Elsevier
Denisov, D. V.Rudominskiy, A. E.Parfeniev, R. V.Shamshur, D. V....
1页原文链接:- NSTL
- Elsevier
